JPH0363495B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention is a blow molding method that can partially provide thick-walled parts, and more specifically, a parison is partially doubled and molded so that the thick-walled parts are integrated during molding. This is a method for manufacturing a hollow body having a thick-walled tubular part.

Elastic air bladders, such as blood pressure measurement bags or lumbar supports for automobile seats, have conventionally been made of rubber. However, when molding rubber,
Since it requires a vulcanization process, the productivity is very low, and the time required for production is long, so the product obtained is also expensive. Therefore, bags are now being made of thermoplastic elastomers, which are highly productive and do not require a vulcanization process. There are two methods of molding the thermoplastic elastomer that is the material of this bag: a method of making a sheet and high-frequency welding, and a method of blow molding.
The elasticity of sheets that can be welded is limited, and the elasticity of thermoplastic elastomers used in comparison with rubber is significantly lower, so rubber cannot be used as a substitute. On the other hand, with blow molding, it is possible to mass-produce products equivalent to those made of rubber, but with blow molding, it is not possible to form a part thicker than the thickness of the parison, so air is supplied from other parts such as rubber tubes. When connecting the tubes to the bag, these rubber tubes are inserted into the air supply opening of the bag and bonded or high-frequency welded. This secondary processing was very complicated, and the adhesive sometimes oozed out, and the welded parts were thermally deformed and deteriorated, making some products unusable. The present invention was invented in view of this point, and its purpose is to obtain a thick part such as a part that forms an air inlet in one piece during molding, and also to have a beautiful appearance. The objective is to obtain a hollow body having a thick-walled tubular portion with high strength.

The case where the present invention is used in a blood pressure measuring bag will be explained below with reference to the drawings. FIG. 1 is a perspective view of a blood pressure measuring bag 1 obtained according to the present invention. 2 is
In the main body, 3 is an air inlet that introduces pressure into the main body. The air inlet 3 is approximately twice as thick as the main body 2, and is integrally connected to the main body 2 as a hollow tube.

Next, the blow molding method of the present invention will be explained based on the drawings. First, the molds 4a and 4b having the external shape of a desired bag on their mold surfaces are separated so that their mold surfaces face each other. A cylindrical parison 5 is suspended between the molds 4a and 4b, and the hanging is stopped when the lower part of the parison 5 reaches the lower part of the mold. Next, the blowing nozzle 7 located outside the molds 4a and 4b is made to protrude in a direction perpendicular to the hanging direction of the parison and the mold clamping direction, and the area of the parison 5 where the blowing nozzle 7 contacts is pushed into the inside of the parison. . Here, the blowing nozzle 7 is made of a double tube, and the tip of the inner nozzle is formed into a split bamboo shape, and the inner nozzle is fitted into the tube by means such as an air cylinder so that it can freely protrude. The blow nozzle 7 itself has a structure that allows the blow nozzle 7 to be moved by appropriate means. It has a mechanism for further protruding the nozzle and ejecting compressed fluid from the inner nozzle at that time.

Next, mold clamping is started, and as mold clamping progresses, the molds 4a and 4b come into contact with the parison 5, and as the parison 5 is flattened, the parison 5 is pushed by the blowing nozzle 7, and the part that has entered the inside of the parison 5 becomes flat. It is folded back and placed around the blow nozzle 7. As the mold clamping progresses further, parisons 51 and 52 that are folded back and overlapped exist around the blowing nozzle, as shown in FIGS. 5 to 7 near the blowing nozzle 7 (see FIG. 5). condition), and the parison 51, 5 overlapped after mold clamping is completed
2 is welded and the parison around the blowing nozzle 7 becomes thick (as shown in FIG. 6). Next, the inner nozzle 7
2 protrudes inward of the parison, pierces the parison covering the tip of the blowing nozzle, and jets compressed fluid from the inner nozzle 72, bringing the parison into contact with the surface of the cavity 8 (the state shown in FIG. 7). After the cooling time has elapsed, the jetting of the compressed fluid is stopped, and the blowing nozzle is pulled out from the thick portion. Next, the mold is opened and the excess parison 5a is removed to complete the bag manufacturing method.

In the blowing nozzle shown in the example, the double tube body moves inward of the mold as described above, and the inner nozzle moves further inside the mold independently of the outer nozzle to blow compressed fluid. For example, as shown in Fig. 8, the structure is such that two air cylinders A and B are arranged in series, air cylinder B moves air cylinder A, and air cylinder A moves air cylinder A. The parison may be pierced and compressed fluid may be injected. Structurally, the cylinder rod 77 of the air cylinder B is fixed to the center of the head cover 73 of the air cylinder A, and the entire air cylinder A can be moved by the air cylinder B. That is, by injecting air pressure into the inlet/exhaust port 74b, the air cylinder A protrudes forward, and conversely, by injecting air pressure into the inlet/outlet port 74c, the air cylinder A moves backward. Air cylinder A rod cover 75
A tubular outer nozzle 71 is fixed to the air cylinder A so that the central axis thereof is the same as that of the air cylinder A.
An inner nozzle 72 is fixed to the piston,
These two nozzles 71 and 72 have a sliding mechanism. Inner nozzle tip 76
The air cylinder A is pointed like a bamboo crack, and the stroke of the air cylinder A is set so that it is housed in the outer nozzle 71 when the inner nozzle 72 is retracted.

In the present invention, any synthetic resin material that can be blow molded can be used. In addition, in order to manufacture an elastically moldable bag as in the embodiment, materials such as soft polyvinyl chloride, polyester elastomer, polyurethane elastomer, polyamide elastomer, olefin elastomer, styrene elastomer, etc. can be used. As soft polyvinyl chloride, the average degree of polymerization is 800~
12,000, preferably 1,500 to 10,000 of polyvinyl chloride, and 30 to 220 of polyvinyl chloride per 100 parts by weight of the polyvinyl chloride.
Parts by weight, preferably 50 to 200 parts by weight, are desirable. If the average degree of polymerization of the polyvinyl chloride is less than 800, mechanical strength such as tensile strength will decrease, while if it exceeds 12,000, the surface appearance of the parison during molding will be poor and the moldability will be extremely poor. Furthermore, if the amount of plasticizer added to the polyvinyl chloride is less than 30 parts by weight, the molded product will become inelastic, while if it exceeds 220 parts by weight, mechanical strength such as tensile strength will be significantly reduced. Various other fillers, stabilizers, stabilizing aids, pigments, etc. can also be appropriately blended into the above-mentioned soft polyvinyl chloride.

As described above, the present invention suspends a parison between opposed and spaced molds, causes a blowing nozzle to protrude in a direction perpendicular to the direction in which the parison hangs down, pushes the parison inward, and tightens the mold, By positioning the folded and overlapped parison around the blow nozzle using the mold and completing mold clamping, the parison is welded into a thick wall to form a thick-walled tubular part near the blow nozzle, and is further compressed by the blow nozzle. Since this method of manufacturing a hollow body having a thick-walled tubular part is characterized by inflating the parison by ejecting fluid, even if the molded product is thin-walled as a whole, it can be made thick-walled in some parts. Particularly when installed in the bag body, it is possible to form a thick air inlet, so when connecting an air supply pipe such as a rubber tube to the bag body from another part, simply press-fit a metal pipe or the like to intervene. They can be airtightly connected by simply attaching them, eliminate the need for secondary processing such as gluing or welding, and have a beautiful appearance as they are integrally molded.

[Brief explanation of drawings]

FIG. 1 is a perspective view of a blood pressure measuring bag obtained according to the present invention, FIGS. 2 to 7 are for explaining the steps of the present invention, and FIG. 2 is a cross-sectional view showing the parison hanging down. , FIG. 3 is a view seen from the side A-A in FIG. 2, and FIG. 4 is a cross-sectional view showing when the blowing nozzle is protruding.
FIG. 5 is a cross-sectional view of the vicinity of the blowing nozzle before mold clamping is completed, FIG. 6 is a cross-sectional view of the vicinity of the blowing nozzle when mold clamping is completed, and FIG. 7 is a cross-sectional view of the vicinity of the blowing nozzle during blowing. FIG. 8 is a partially sectional view illustrating the mechanism of the blow nozzle. 1: Bag for blood pressure measurement, 4a, 4b: Mold, 5:
Parison, 7: Blowing nozzle.

Claims (1)

[Claims] 1 A parison is suspended between opposing molds,
A blowing nozzle is made to protrude in a direction perpendicular to the hanging direction of the parison, the parison is pushed inward, and the mold is tightened, and the parison near the blowing nozzle is flattened by the mold and folded back around the blowing nozzle. By positioning the overlapped parisons and completing mold clamping, the parisons are welded into a thick wall to form a thick-walled tubular portion near the blowing nozzle, and compressed fluid is ejected from the blowing nozzle to expand the parison. A method for manufacturing a hollow body having a characteristic thick-walled tubular portion.